An inflatable vehicle occupant protection device, such as an air bag, is inflated when a vehicle experiences a crash. Inflation fluid is directed to flow from an inflator into the air bag to inflate the air bag. When the air bag is inflated, it extends into the vehicle occupant compartment to help protect an occupant of the vehicle from forceful impact with parts of the vehicle.
Some inflators are known as dual stage inflators. A dual stage inflator typically provides for two different inflation fluid flow rates into the air bag. The initial inflation fluid flow rate into the air bag is a relatively low rate and thereafter the fluid flow rate increases.